21644444543 has 4 divisors (see below), whose sum is σ = 21681318120. Its totient is φ = 21607570968.

The previous prime is 21644444539. The next prime is 21644444551. The reversal of 21644444543 is 34544444612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21644444543 - 2² = 21644444539 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21644444543.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21644444573) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18435908 + ... + 18437081.

It is an arithmetic number, because the mean of its divisors is an integer number (5420329530).

Almost surely, 2^21644444543 is an apocalyptic number.

21644444543 is a deficient number, since it is larger than the sum of its proper divisors (36873577).

21644444543 is an equidigital number, since it uses as much as digits as its factorization.

21644444543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36873576.

The product of its digits is 737280, while the sum is 41.

The spelling of 21644444543 in words is "twenty-one billion, six hundred forty-four million, four hundred forty-four thousand, five hundred forty-three".